The Keystone XL pipeline, which Steyer and Lynch’s Democratic rival, Ed Markey, oppose but Lynch supports, is a serious issue deserving serious debate. But it shouldn’t be reduced to a litmus test, especially under the threat of an onslaught of unregulated campaign spending. Both Lynch and Markey have agreed to block outside groups from advertising in the race under the so-called “people’s pledge.” Steyer may seek to evade that pledge by focusing on other forms of political spending — such as “guerrilla marketing” and door-to-door campaigning — but his threat against Lynch surely violates the spirit of the pledge. Markey should tell Steyer to back off.

In last year’s Warren-Brown race, the people’s pledge largely succeeded in keeping super PACs and their big-money donors out of the state. One of the agreement’s vital benefits was that it forced candidates to take responsibility for campaigning done on their behalf. No longer could they hide behind the nominal independence of billionaire donors as those backers did the candidates’ dirty work for them — exactly what Steyer seems to be threatening to do now on Markey’s behalf.

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